Process for mesophilic or thermophilic aerobico-enzymic conditioning of liquid organic substances and biomass

Abstract

The invention relates to the conditioning of liquid organic substances and biomass, particularly of municipal sewage sludge, with the help of chelating agents and enzymes, by breaking the organic substance down in an aerobic-conditioning reactor by addition of chelating agents and enzymes, this is discontinued prior to the complete dissolution of the organic matter after a time period of 0.5 to 20 hours. The mixture of substances is then subjected to an open-top non-aerated postreaction phase of 5 to 15 hours during which biogenous flocculation takes place. A solid-liquid separation follows.

We claim: 
     
       1. A process for the enzymatic, aerobic conditioning of a liquid containing organic matter, comprising contacting in an aerobic reaction said liquid with from about 0.001% to about 0.1% wt. based on the organic matter content dry basis of said liquid of a chelating agent, and with from about 0.001% to about 1.5% wt. same basis of one or more enzymes adapted to break down said organic matter, aerating the resulting mixture, and terminating said aerobic reaction when from about 30% to about 50% wt. of the particles of said organic matter are smaller than 1μm, and from about 40% to about 70% wt. of the particles of said organic matter are smaller than 5μm, and subjecting said mixture to a nonaerated postreaction phase until from about 15% to about 20% wt. of said particles are smaller than 1μm, and from about 30% to about 40% wt. of said particles are smaller than 5μm, and then recovering the solids content of the mixture by separation of its liquid content. 
     
     
       2. The process of claim 1, wherein said chelating agent is a salt of nitrilotriacetic acid. 
     
     
       3. The process of claim 1, further comprising separating a part of the solids content of the liquid to be treated before or after the adding of the chelating agent, liberating enzymes in said solids, and returning said solids with said liberated enzymes, to the process. 
     
     
       4. The process of claim 1, further comprising adding one or more of conditioning agents, polymeric flocculants, and precipitants to the process before, during, and after said step of aerating. 
     
     
       5. The process of claim 1, further comprising heating by exothermic reaction heat and/or by added heat the reaction mixture after said step of aeration. 
     
     
       6. The process of claim 1, wherein the aerobic reaction takes place in from about 0.5 to about 20 hours. 
     
     
       7. The process of claim 1, wherein said postreaction phase takes place within from about 5 to about 15 hours. 
     
     
       8. The process of claim 1, wherein said postreaction phase is conducted at an elevated temperature of up to 75° C.